One prior approach for removal of DI water (deionized water) from silicon materials required very large, long, expensive hot air conveyor belt dryers that were fairly ineffective and that could only produce dried polysilicon material in a reasonable period of time if the material were heated to temperatures making the material difficult to handle by operators. The volume of recycled material in a wafer and/or solar cell processing line is so large that such hot air dryers must be extremely long to completely dry a basket of polysilicon material in a reasonable period of time, typically requiring a material residence time of approximately thirty minutes in order to achieve an output rate of one basket every six minutes. This rate of drying is necessary for practical operation. These long dryers take up a considerable amount of production floor space. In addition the process of drying with hot air accelerates native oxide growth during the dry cycle. The standards for minimum purity levels of the recycled polysilicon material continue to increase and the presence of native oxide can make it difficult to satisfy these increasing purity requirements.
Another known method to remove the moisture from these materials is to utilize a vacuum chamber to reduce atmospheric pressure and force the water to boil at room temperature. Although this method provides material that is cool to the touch, there have been issues with the material being frozen in the center and ineffective drying in that some product tends to remain wet. Also, it is extremely difficult to remove large quantities of water using only a vacuum chamber, as the process transitions from one of rapid, flash vaporization to slow sublimation once all the sensible heat above 0° C. is removed. Therefore this approach is less than satisfactory.